Soil microplastics – current research trends and challenges: preliminary results of the earthworm Eisenia fetida impact on glitters

This paper shortly introduces the topic of soil microplastics by presenting a comprehensive review of the current state of the art in this field. It focuses mainly on the role of primary microplastics, particularly glitters, due to their large surface-to-volume ratio. From conclusions about current challenges and research directions, after analysis of the crucial “knowledge gaps “, one can point out the lack of a detailed description of the influence of microplastics on biota. The earthworms are promising model organisms that may play in soil ecosystems a similar role to the bivalves in waters. Thus, this mainly review paper was enlarged by the preliminary results of studies on glitters and bioglitters naturally aged in milli-Q water and soil with Eisenia fetida. Fourier-transform Infrared (FTIR, microscopy in the reflectance mode) and Raman spectroscopy (780 nm) were used to identify the subsequent notable changes in studied materials. The presence of the polymer (PET) core in the standard glitter particles is confirmed. In addition, the leakage of dyes from bioglitters was observed within the 9-week experiment. Tested bioglitters decompose in a slightly different way. Blue and pink pigments had entirely different stability as only one disappeared without a trace under UV light (blu), and the other remained stable in solution, confirmed by UV-Vis spectra. The nephelometry shows sedimentation of glitters after turbulent agents in the environment. This paper presents the natural weathering of primary microplastics in the presence of Eisenia fetida.